Vacuum cleaner



P 1, 1952 G. E. LOFGREN ET AL 2,591,567

VACUUM CLEANER 6 Sheets-Sheet 1 Filed May 29, 1948 INVENTORS GUSTAF EINAR LOFGREN AXEL PETERSON 51. 0

ATTORNEK April 1, 1952 e. E. LOFGREN ET AL 5 5 VACUUM CLEANER Filed May 29, 1948 6 Sheets-Sheet 2 IN VEN T 0R5 GUSUIF EJNAR LOFGREN AXEL PETERSON ATTORNEY April 1, 1952 G. E. LOFGREN ET AL 2,591,567

VACUUM CLEANER Filed May 29, 1948 6 Sheets-Sheet 3 IN VENT 0R5 QUSMF EINAR LOFGREN AXEL PETERSON April 9 2 G. E. LOFGREN ET AL 2,591,567

VACUUM CLEANER Filed May 29, 1948 6 Sheets-Sheet 4 fl'y. 4

H 71 95 I y [N VEN TORS GUSTAF E/NAR LOFGREN AXEL PETERSON BW%Q AT TORNEK April 1952 G. E. LOFGREN ETAL 2,591,567

VACUUM CLEANER Filed May 29, 1948 6 Sheets-Sheet 6 x 164 V i 5 j; 5 j 16M, 73

I x 11m [2/ IINVENTORS GUSTAF EINAR} LOFG'REN AXEL PETERSON ATTORNEY Patented Apr. 1, 1952 VACUUDI CLEANER Gustaf Einar Lofgren, Wesskum Wood, Riverside, and Axel Peterson, Stamford, Conn, assignors to Electrolux Corporation, Old Greenwich, Conn., a corporation of Delaware Application May 29, 1948, Serial No. 29,964

This invention relates to a vacuum or suction type cleaner adapted for use as an industrial or similar large scale cleaning device for hotels, apartment houses, hospitals and the like. More particularly it embraces an automatically conditioned unit of large capacity and one which maintains itself operating at maximum emciency by means of self-contained control mechanisms.

Heretofore considerable difficulty has been experienced in maintaining the operation of vacuum cleaners at optimum efiiciency, particularly inindustrial usage where various types and sizes of dust particles are picked up, some of which particles clog the conventional filtering devices most commonly used after but a short interval of use. Invariably, the flexible cloth or paper bag forming the dust separating element of the conventional vacuum cleaner unit shows progressively decreasing efiiciency with use due principally to surface adhering and internally entrapped dust particles which close the interstices of the particular dust filtering or separating element used.

It is a major object of this invention to provide improved means for dislodging dirt, dust and foreign matter accumulated on and between the interstices of the fabric or other material used to filter out foreign matter from the air stream coursing through the filter screen.

A further and important object is to provide a new and improved type of suction cleaner wherein the source of suction is automatically diverted upon the attainment of a predetermined condition or change in the air pressure characteristics within the various cleaner compartments, whereupon the dust collecting and screening or dust separating action is discontinued and an auxiliary unit is brought into operation to effect an agitation of the screen of such intensity and duration that the adhering dust particles are dislodged from the interstices and separated out of the general path of the air current and deposited into a receptacle or dust chamber of comparatively large capacity for subsequent removal.

Still another object is to provide a large scale vacuum cleaner which is light and readily maneuvered as by the cleaning hose or flexible wand connection without necessitating the provision of additional or auxiliary handling means.

A still further object is to provide a cleaner having an unusually large dust capacity.

It is an additional object of this invention to provide a vacuum cleaner having a large capacity dust or dirt settling chamber into which the dust 18 Claims. (Cl. 183-54) I collected is readily deposited from the surface of its filter cloth.

A further object is to provide a dust or dirt canister which is housed in the base of the cleaner apparatus and which is readily removable therefrom for disposal of the accumulated dirt.

A further object is to provide means for removing dust adhering to a dust collecting screen filter member, the dust being loosened therefrom and removed from contact therewith without necessitating dismantling of the cleaner unit.

Still other and further objects will be disclosed below or will become obvious from a study of the followin description together with the accompanying drawings wherein:

Fig. 1 is a vertical sectional view taken along the line I-l of Fig. 3;

Fig. 2 is a plan view of the rear end of the cleaner of Fig. 1 taken from the right-hand side thereof;

Fig. 3 is a top plan view of the cleaner of Fig. 1 with the cover thereof removed;

Fig. 4 is a sectional View taken on the line 44 of Fig. 1;

Fig. 5 is a view of the solenoidal spring biased valve actuating mechanism;

Fig. 6 is a sectional view through the air actuated switching mechanism of Fig. 1;

Fig. '7 is a diagrammatic illustration of the wiring connections; and

Fig. 8 is a diagrammatic sketch of the pneumatic tubular connections for the operation of the automatic controls.

It is a feature of this invention that provision is made for automatically utilizing an air pressure or suction operated agitator for shaking a clogged filter screen element in order to dislodge dust therefrom. In a specific embodiment, the air flow or suction for the operation of the agitator is shown as provided by the usual vacuum cleaner motor fan unit, the air suction from which is completely out off or diverted from its dust collecting function and instead is used to operate a screen agitating device, preferably by means of an intermediate air suction operated turbine or similarly air driven device. In a preferred embodiment the turbine drives an eccentric which shakes a screen support to knock the adhering dust and dirt loose from the clogged dust screen. This loosedirt then drops through a dead or motionless air space into a receptacle for collection and subsequent disposal without being subjected to such disturbing air currents as are incident upon and accompany the normal cleaning operation during which air suction is 3 effected through the filtering screen. The result is practically complete dislodgement of most of the adhering and clogging dust particles and the reestablishment of an efficient, high speed air suction for the subsequent dust collecting operation of the cleaner.

In the past it has been found that such dirt and dust adhering to the screen and in the interstices of the screen and on the fibers thereof greatly impairs the dust separating and. cleaning efliciency of the cleaner unit. In the embodiment of the invention herein disclosed, the thorough shaking or agitation of the screen effectively loosens any adherent or accumulated dirt from the surface of the screen. This agitation of the screen is effected by an eccentrically driven shaking device which in a preferred type of construction is powered by an air actuated turbine, the eccentric causing a rotation in the nature of a gyratory oscillation of a plate supporting the dust separating screen or dust bag. This shakes most, if not all of the adhering dust particles loose. The most effective dust removal possible is-attained when no air courses through the screen filter during the shaking interval. Then the losened particles can readily fall by gravity to the bottom of the dust receptacle and out of the general path of the vacuum cleaner air current.

The shaking device is essentially a turbine comprising air current driven blades mounted on a rotor plate which is used to revolve an eccentric mounted on a common shaft. An improved valve mechanism is used to operate, selectively, the cleaner cycle or the filter screen agitating cycle. The valve arrangement is such that air flow through the dust chamber is discontinued and instead an air current is established to operate the turbine which agitates the dust separating filter screen and restores its dust removal efficiency.

The entire operation is automatic and effected by the movement of air current control valves which are normally spring biased to vacuum cleaner position and are shifted automatically under predetermined conditions in order to terminate all air flow or suction through the dust chamber and screen filter member and to initiate air flow or suction over the turbine blades to effect the dust disengaging or shaking step whereby the original dust removing efiiciency of the screen filter cloth is restored for subsequent vacuum cleaner operation.

" Referring now more particularly to the drawings, the vacuum cleaner housing I is of tear drop or streamlined design and may conveniently be fabricated from a number of castings suitably "screwed, riveted or otherwise fastened to ether and sealed at the joints against air leakage by means of suitable gaskets. Thus the cleaner comprises an inlet housing II having an air inlet tube I2 connected by a rubber hose I3 and suitable sleeves to inlet port I4 which opens somewhat tangentially into dust chamber ring 25. These units are appropriately supported on the vertical walls of a base I30 which is open at the top and bottom except for transverse cross brac- "ing members I3I. A motor fan unit I32 is resiliently supported from housing I0, the lower portion of the unit being disposed in a compartment I33 formed in base I30, the bottom of the compartment being sealed by motor plate cover I34; An air outlet tube I35 is connected to compartment I33 by means of a flexible coupling I36 and extends to the rear of base I30. A

removable dust container or dust receptacle 30, sealed tightly against the lower rim portion of dust chamber ring by gasket 3|, is also supported by suitable means in the base I30. Finally th base I is supported on three ball bearing wheels, two at the rear, one of which is shown at I40, and one caster I4I mounted at the front end by bracket I42.

Top casting has means for mounting the reentrant frusto-conical filter screen 4I, turbine assembly 60, air conduits I0, 'II and valve housing 12. The vacuum cleaner unit is provided with a removable hood I which may have a handle integral therewith or folded into an opening therein as shown at I5I.

The cleaner unit is provided with a flexible hose I5 fitted into a coupling [5 at the front or outer end of conduit I2. The flexible hose provides the means by which the cleaner is moved or pulled across the floor. No device for pushing thecleaner unit is necessary since the ball bearing Wheels I40 on each side of the body together with the swivel mounted front wheel I4I make for easy rolling motion in any direction across the floor. The handle I5I which folds into and below the top cover or hood I50 is provided to facilitate carrying the cleaner, such as up and down stairs. A rubber bumper strip I31 around the entire lower portion of the frame base I30 serves to buffer the cleaner against extraneous contacts and prevents scratching and otherwise marring furniture, walls, etc., encountered in its path. The elongated casing has ample room at the rear for the removal canister, dust pan or dust receptacle 30. This receptacle fits tightly into the cleaner frame and is provided with an innertop flange and rubber sealing ring or gasket 3I which forms an air-tight fit with the bottom of cylindrical dust chamber ring 25 when pressed into position by handle 32. This handle includes a pair of arms 33 disposed on either side of the receptacle and pivoted thereto at 34, the outer end of the arms being joined by a transverse hand grip member 35. When the receptacle is in place, within the casing, the inner ends of the arms are disposed above spring biased abutments 36 mounted within the casing, and consequently when the outer end of the handle is raised, the inner ends of the arms bear against the abutments 36 and the entire receptacle is raised so as to resiliently press the gasket 3| against the bottom of ring 25. The handle is retained in raised position by means of a spring latch 31 which engages hand grip member 35.

The internal structure of the automatic vacuum cleaner comprises tube means I2 for conveying dust-laden air to a dust separator unit which is divided into two parts by a filtering area comprising the cloth dust separator M.

The dust separator or filter bag M is of a reentrant frusto-conical form, the various elements of the filter being folded back upon themselves in zig-zag portions when viewed in section. Thus, the outer edge 42 of the cloth forms a large open mouthed section which is secured to a ring 43 which in turn is provided with a rubber packing or sealing material 44, the edge 42 being held firmly in place by dust bag spacer 45. The filter cloth extends upwards and inwards from edge 42 to form an external frusto-conical section 46, the upper and smaller end of which is secured at 4! to a normally stationary supporting plate from which the filter screen cloth extends downwardly and inwardly to form an inner frustoconical section 48. The folds 41 are held in flanges on the outer edge of plate 65 by a split retaining ring 49 which may be collapsed and inserted therein and then expanded to bring the ends into engagement and finally locked into position, clamping the dust separator firmly in place.

The downwardly disposed inner fold 48 forms an innermost reentrant frusto-conical portion 50 which is secured at its inneropen end to a ring 5| which in turn is fastened by spring clips 52 to the plate 65. A final cup-shaped segment either of rubber or filter cloth 53 is aflixed at its outer edge by spring clips 52 and at its center by the upper end of deflector 26 and machine screw 21. A toroidal separator 54 of metal screen meshwork or of joined rubber sections is suspended freely between folds 48 and 50 to keep these respective frusto-conical portions distended and free from collapse during the passage of air there-' through.

The air current in its course enters one portion of the dust chamber, goes through the filter 4| where dust particles are excluded from the air stream, and the dust free air is then drawn by suction through exit conduit I into a compartment 73 in casting I| into, which extends the upper end of motor fan unit I32. From here the air is drawn through the motor fan unit and is exhausted through conduit I35. A flexible diaphragm I38 separates chamber I3 from chamber I33. A second normally closed conduit II also connecting with the exhaust or suction chamber I3 of the motor fan unit supplies the necessary air suction when valve I5 is open to operate an air driven filter cloth shaking device 60. This valve I5 is mounted on a common spindle IS with a valve I4 which latter valve controls the air flow through conduit I0, the valves being so arranged that when one is open the other is closed.

Automatic means is provided to operate a valve switching mechanism shown in Fig. 6, which is responsive to the establishment of predetermined air pressure conditions within the cleaner to terminate the vacuum cleaner cycle and effect the filter screen cleaning cycle of operations. The air pressure changes necessary to effect this switching to the screen cleaning cycle result from the continued use of the cleaner as a dust gathering device. Then, after a second predetermined condition, usually the lapse of a certain time interval of operation of the screen shaking device, the automatic switching mean returns the cleaner to its former mode of operation as a vacuum cleaner or dust collector. In the then relatively dust free condition of the filter, the vacuum cleaner is thereafter capable of a correspondingly highly eflicient dust collecting operation. This continues until the filter screen clogs with dust, whereupon the filter agitating cycle is repeated.

In a normal dust collecting cycle of operations,

dust-laden air enters through air inlet tube I2 and flows tangentially around and upwardly over the inner border of the cylindrical upper dust chamber 25 immediately above the large dust receptacle 30. As the air velocity decreases and simultaneously changes its direction after leaving opening I4, the heavier dust particles are deposited out of the decelerated air stream and fan downward into the dust receptacle 30 where they are collected for subsequent disposal.

A curved deflecting plate 26 is secured to the under side of the bag mount by machine screw 21. Dust-laden air striking this deflecting plate 26 is diverted sidewise and upward to form a tangentially and helically swirling stream of air in the form oi an upwardly disposed spiral air column. The incoming air current is hence caused to flow upwards and against the filter cloth 4|. Thus any dust remaining entrained in the air stream is carried along until separated out by contacting the screen filter cloth 4|, the surface of which serves to stop and separate out the remaining dust particles, while the air current itself proceeds through the filter openings to the exhaust conduit.

The somewhat tangentially disposed entry port l4 for the incoming air stream accentuates this type of air swirling action. This air current also results in the formation of horizontally disposed spiral air currents of progressively and down wardly decreasing intensity in the canister 30. Thus the baflle plate 26 and the tangential entry port I4 tend to keep the incoming air swirling in horizontal planes, thereby further facilitating the settling out of the heavier dust particles, all without undulydisturbing the dust already settled or deposited on the bottom of the canister. The air in the canister 30, as compared to the air in the upper part of the dust chamber, is relatively immobilized and particularly so towards the bottom of the settling chamber. At most, it rotates or swirls at a progressively decreasing velocity'as it approaches the surface of the dust deposited in the bottom of container 30.

This type of construction makes it possible to precipitate the heavy particles out of the incoming air stream with a maximum of efiiciency and deposit them in the canister or dust receptacle container 30. In this way the heavy particles are kept from physically contacting and possibly abrading dust bag filter cloth 4| which separates the dust canister 30 from the motor fan unit I32.

The motor fan unit I32 draws the filtered air upwardly through the filter cloth 4| by way of connecting conduit 10 when the valves are in the position shown, Fig. '1, with valve I4 open and valve '15 closed.

Any continuous operation of the cleaner unit or operation over many intermittent periods. causes the filter cloth 4| to become coated and clogged with dust and as a result the air pressure in the region between the filter cloth 4| and the motor fan unit I32 becomes progressively lower and lower. An opening 11 into this increasing vacuum or decreasing pressure region connects directly through rubber tube III], Fig. 8, to an air actuated valve operating mechanism 80, Fig. 6 (described in more detail below) which operates at a predeterminable point to trip a microswitch which in turn closes a circuit to energize solenoid I00. Plunger I III of solenoid I00 actuates spring link I02 against the bias of spring I04 and causes the valve arm I03 on spindle I6 to change the position of butterfly valves I4 and I5 whereby valve I4 closes and valve I5 opens. This, respectively, terminates all air flow through the air filtering screen cloth 4| and initiates the fiow of a current of air through exhaust conduit II which connects directly to air turbine 60 causing the latter to rotate.

Air turbine 60 includes a rotor 6| which drives a shaft 63 and an eccentric 64 afiixed on the shaft. Thus, the opening of valve I5 causes a current of air to flow through conduit II and drives the turbine 60. This, in turn, causes screen filter cloth or dust bag holding plate 65 mounted by needle bearings 66 on eccentric 64 to undergo a gyratory rotation, whereupon'dust and dirt particles attached to the filter cloth 4| are shaken loose and fall downwardly by gravity to be collected in receptacle 38. A counterbalance 61 mounted to rotate with the eccentric 64 prevents any excessive vibration being transmitted throughout the body of the cleaner unit. Turbine blades 68 integral with rotor 6| are driven by the air current entering through inlet ports 69.

The air pressure actuated valve control unit 88 comprises an air pressure actuated switching device shown in sectional view in Fig. 6. This control unit is responsive to predetermined changes in air pressure within the cleaner unit to operate a switch 90 which serves to make and break a circuit for energizing and deenergizing solenoid |08. The latter, operating through plunger |8| and link I82, positions the valves for the selective operation of the correspondingly associated air powered devices.

In further detail, the assembly control unit 88 comprises a mounting framework which includes a lower housing 8|, an upper housing 82 and a pair of diaphragms 83 and 84 pneumatically sealed therein and separated by a ring member 85 to form three air chambers 86, 81, and 88. The outer two chambers, 86 and 88, are connected together by a common duct 89. This duct 89 is connected at opening 11 to the exhaust or outlet conduit 18 of the dustchamber through an appropriately adjusted needle valve 89a. and rubber tube ||0.- As the filter cloth 4| becomes clogged, the pressure decreases in the exhaust outlet conduit 18 to which the two outer air chambers of the control unit are connected. The inner or central air chamber 81 is connected at opening l9 to the inlet conduit |2 through an appropriately adjusted needle valve 19a and rubber tube This enables diaphragm 84 separating chambers 81 and 88 to measure pressure difierences communicated from the respective sides of the filter screen 4 I.

It is to be noted that the increased clogging efiect of the dust particles on the filter screen cloth 4| resulting from the continued use of the cleaner unit, although producing a progressive pressure decrease on the clean or outlet side of the filter screen 4|, simultaneously results in a. pressure increase approaching as a limit normal atmospheric pressure on the dusty or inlet side of the filter screen. These two pressures are transmitted through tubes H8 and I, respectively, to the opposite sides of diaphragm 84. When this pressure difiference reaches a predetermined valve, for all practical purposes equivalent to a 20 inch column of water, control unit 88 trips switch 98 and initiates the screen shaking cycle.

In more detail, this is effected as follows: during the vacuum cleaning operation the progressively decreasing pressure in the exhaust conduit 'lfl'caused by the continuing dust collection and its further clogging of the filter screen 4| is communicated through tube ||8 to the two outer chambers 88, 88 of the control unit 88. Simultaneously, the slightly increasing pressure in conduit I2 is communicated to chamber 81 through tube whereupon the diaphragms 83 and 84 move farther and farther apart. At a predetermined pressure difference, pin 89 actuated from the center of the upper diaphragm and biased by spring 9|, actuates pin 92 through sealing diaphragm 93. whereupon microswitch 98 is tripped to close a circuit for energization of the valve actuating solenoid |08.- Then valve 14 is moved to closed position to discontinue the air current flow through the filter cloth 4| and terminate the vacuum cleaning operation, and .simultaneously valve 15 is opened and the air current flow is diverted through conduit II to operate turbine 88. Thereupon air is exhausted from bellows 95 through an appropriately adjusted, needle valve 98a and rubber tube 2 connected to opening 78 in exhaust conduit 1| and after a predetermined time interval com pletely collapses the bellows 95. At this point, projection 98 carried by the upper end of bele, lows 95 being lowered to contact pin 91 of microswitch 98 resets the latter and breaks the circuit, deenergizi ng solenoid me. Then, with the reclosure of valve 15, tube 98 is opened to atmospheric pressure through tube ||2, opening 18 of conduit H, and the inlet ports 69 of turbine 69,

and bellows 95 fills up with air once ,again u'nder the expansion action of spring 99 interior thereto. Thus, the valves 14 and 15 are returned to their spring biased positions, the assembly control unit 88 is reset and the entire apparatus is ready for more efficient vacuum cleaner operation once again.

It may happen, however, that unless special provisions are made compensating for or delaying the transmission of sudden pressure changes in the interior of the cleaner to the unit 88, a,

sudden surge or gust of air mayv "result in an unwarranted tripping of the switch mechanism. Such sudden gusts usually resulting from the sealing of an operatively associated nozzle .such as l5, followed by a sudden unsealing of the nozzle, such as accompanies its being pressed against the floor, Wall or the like, followed by its sudden release. In order to prevent any such unwarranted operation of the switching mechanism, constricted orifices in the form of needle valves 79a, 89a, and 980. are provided'in the lines .||9, etc. communicating these pressure changes to the chambers 86, 81, 88. Thus, all sudden pressure changes do not immediately act upon the diaphragm 84 but must awaitthe establishment of what may appropriately be termed a steady state.

In addition to the use of restricted orificesj or apertures, a further assurance against unnecessary interruptions of the cleaning operation by an unwarranted tripping of the switch mechanism 98 is eiiected by the provision of a Weaker biasing spring on the lower diaphragm 83'than that used to bias the upper diaphragm 84. With this arrangement any sudden pressure increase in chamber 8?, such as that caused by the sudden release of a sealednozzle i5, results in a movement of diaphragm 83 compressing its weak spring and effecting a pumping action whereby air contained in chamber 86 is forced through common duct 89 into upper chamber 88 where it serves to further brace or bias diaphragm 84 againstany movement tending to trip switch same auxiliary devices serve to buffer or delay the response of diaphragm 83 by acting in a corresponding though inverse manner when the sealed nozzle is suddenly lifted, the resumption of air flow load through the cleaner serving to decelerate the motor speed with a correspondingly great increase in air pressure in the various portions of the dust chamber.

It is to be noted that under most operating conditions, the resistance ofiered by the filter screen 4I itself, unaided by the increase in resistance effected by entrapped dust particles, is suflicient to eifect some slight movement or bellowing of diaphragm 83 against its biasing spring before any motion is imparted to diaphragm 84. All of these advantages and others not specifically mentioned result in a highly flexible control unit capable of absorbing and leveling out both large and small sudden pressure variations, and one which is responsive only when the pressure differences attain the conditions of an established steady state well within a predetermined margin embracing that maximum pressure difference previously calculated as necessary and desirable for the actuation of switch 90. Such a device avoids the many inconveniences usually accompanying too frequent filter shaking with its interruption of the vacuum cleaning process. It also avoids the necessity of excessively accurate setting of the controls, the

provision of tolerances for variations in the frictional engagement of moving parts as well as operational changes caused by the above-mentioned pressure surges, shocks and blows.

The various portions of the control unit are sealed against leakage by means of rubber cement gaskets and are variously otherwise adapted for efiicient operation. The electrical control circuits and the pneumatic connections for effecting control are shown in Figs. '7 and 3, respectively.

The wiring diagram, Fig. '7, shows the current source in the form of a conventional plug-in cord I60, a switch I6I and wires I62 connecting the current source to terminal block I53. Conductors I 64 energize the motor fan unit I 32 upon closure of switch I BI Conductor IE5 goes to one terminal of solenoid I08, while conductor I66 goes to one conductor of the on and oif switch in control assembly unit 80. Terminal I6! completes the connection from the control unit 80 to the solenoid I00.

Upon the establishment of a predetermined pressure difference, as above described within the cleaner the circuit is closed for the energization of solenoid I00 and consequent operation of the filter cloth cleaning cycle, as previously eX- plained. The changes in pressure conditions are communicated through the pneumatic tubular connections for the operation of the automatic controls more clearly illustrated in Fig. 8 where the assembly control unit 80 is shown somewhat out of position in order to indicate the association of the various elements more clearly. The common duct 89 between the two outer chambers 86 and 88 is connected by rubber tube II!) to opening 11 in conduit IS. The inner chamber 81 is connected by rubber tube III to opening I9 in air intake conduit 12 and tube 98 adapted to withdraw air from and admit air to the bellows 95 is connected by rubber tube II2 to opening I8 in conduit I I.

Needle valves in each of the pneumatic circuits provide readily adjustable means for controlling the ingress and egress of air and obtaining the desired sensitivity of response and shaking time control, while varying the biasing spring tension of the diaphragms provides a means for, adjusting the pressure difference at which unit will trip switch 96. The functioning of the pneumatic control assembly for the on and ofi operation of microswitch SI] and the consequent energization and deenergization of solenoid I0!) is thus efiiciently and automatically carried out as heretofore described.

Various alternative arrangements and accessory elements are contemplated as equivalent embodiments of the principal invention herein more specifically described and illustrated. Thus the exhaust conduit I35 may readily be made to open out from the front rather than the rear of the vacuum cleaner body II! by arranging an opening through base member I30, bracket I42 and bracket cover I43. Accessory filter pads can also be inserted in the air path between filter cloth II and the entrance of air into the motor fan unit I32 and at any conveniently positioned or readily accessible portion thereof for subsequent replacement. It is also within the comprehension of the inventive concept to vary the action of the valve mechanism substituting more positive setting or completely air or pneumatic actuation for electromagnetic actuation.

Other variations are likewise contemplated. FoneXa-mple, deflector plate 26 may conveniently be turned on its axis through when the vacuum unit is to be used for sopping up water, the deflector then serving to deflect the water directly down into the container 35 and away from the filter cloth bag 4 I.

Thus it is to be understood that the embodiment more fully described and illustrated herein is merely illustrative and not a limited description of the invention since certain changes may be made in the constructions setforth embodying the invention without departing from its scope, and therefore it is intended that all matter contained in the above description, or shown in the accompanying drawings, shall be interpreted as illustrative and not as limiting the scope of the invention and that the latter is to be broadly construed within the purview of the appended claims.

We claim:

1. In a vacuum cleaner, a dust collecting cas ing, an air inlet and an air outlet in the casing, a motor fan unit for producing a flow of air therethrough, means in the casing situated between the air inlet and outlet for filtering dustladen air, means for agitating the filtering means, air driven means for producing power for operating said agitating means, and means responsive to an increase in, dirt contaminating said filtering means for diverting the air flow from the filtering means to operate the air driven means.

2. In a vacuum cleaner, a dust collecting casing, an air inlet and an air outlet in the casing, a,motor fan unit for producing a flow of air therethrough, means in the casing situated between the air inlet and outlet for filtering dustladen air, means for agitating the filtering means, air driven means for producing power for operating said agitatin means, and means responsive to an increase in dirt contaminating said filtering means for diverting the air flow from the filtering means to operate the air driven means, and additional means for terminating the operation of said agitating means and reestabhaust conduit connected with the source of air suction for withdrawing air through said screen and from the outlet section to separate out dust particles on the surface of said screen, means for agitating said screen, means for disconnecting the exhaust conduit from the suction source, means for connecting the suction source to operate said agitating means, and means responsive to the establishment of a predetermined pressure drop within said outlet section to operate said latter two means.

4. In a vacuum cleaner, a source of suction, a dust separating chamber, a dust screen in the chamber dividing it into an inlet and an outlet section, an inlet conduit for conveying dustladen air into the inlet section of said chamber, an exhaust conduit connected with the source of suction for withdrawing air through said screen and from the outlet section to separate out dust particles on the surface of said screen, means for agitating said screen, and means responsive to the establishment of a predetermined pressure drop through said screen for diverting the suction source from the exhaust port to operate the agitating means.

5. In a vacuum cleaner, a source of suction, a dust separating chamber, a dust screen in the chamber dividing it into an inlet and an outlet section, an inlet conduit for conveying dustlade'n air into the inlet section of said chamber, an exhaust conduit connected with the source of suction for Withdrawing air through said screen and from the outlet section to separate out dust particles on the surface of said screen, means for agitating said screen, means responsive to the establishment of a predetermined pressure drop through said screen for diverting the suction source from the exhaust port to operate the agitating means, and means for determining the duration of operation of said lastmentioned means.

6. In a vacuum cleaner, a source of suction, a dust separating chamber, a dust screen in the chamber dividing it into an inlet and an outlet section, an inlet conduit for conveying dustladen air into the inlet section of said chamber, an exhaust conduit connected with the source of suction for withdrawing air through said screen and from the outlet section to separate out dust particles on the surface of said screen, means for agitating said screen, a pair of valves for diverting the suction source from the exhaust conduit to operate the agitating means, and means responsive to a predetermined pressure drop through said screen for actuating said valves.

'7. In a vacuum cleaner, a source of suction, a dust separating chamber, a dust screen in the chamber dividing it into an inlet and an outlet section, an inlet conduit for conveying dustladen air into the inlet section of said chamber, an exhaust conduit connected with the source of suction for withdrawing air through said screen and from the outlet section to separate out dust particles on the surface of said screen, means for agitating said screen, a pair of valves for diverting the suction source from the exhaust conduit to operate the agitating means, and electromagnetic means responsive to a predetermined pres- 12 sure drop through said screen for actuating said valves.

8. In a vacuum cleaner, a source of suction, a dust separating chamber, a dust screen inthe chamber dividing it into an inlet and an outlet section, an inlet conduit for conveying dust-laden air into the inlet section of said chamber, an exhaust conduit connected with the source of suction for withdrawing air through saidscreen and from the outlet section to separate out dust particles on the surface of said screen, means for agitating said screen, a pair of valves for diverting the suction source from the exhaust conduit to operate the agitating means, electromagnetic means for actuating said valves, and pneumatic means responsive to a predetermined change in the air pressures Within the inlet and outlet sections of the dust chamber for energizing the electromagnetic means.

9. In a vacuum cleaner, a source of suction, a dust separating chamber, a dust screen in the chamber dividing it into an inlet and an outlet section, an inlet conduit for conveying dustladen air into the inlet section of said chamber, an exhaust conduit connected with the source of suction for Withdrawing air through said screen and from the outlet section to separate out dust particles on the surface of said screen, means for agitating said screen, a pair of valves for diverting the suction source from the exhaust conduit to operate the agitating means, electromagnetic means for actuating said valves, a circuit, means in said circuit for energizing the electromagnetic means, a switch in said circuit for closing and opening the circuit, and pneumatic means responsive to a predetermined change in the air pressures within the inlet and outlet sections of the dust chamber to actuate said switch for closing said circuit.

10. In a vacuum cleaner, a source of air suction, a dust separating chamber, a dust screen in the chamber dividing it into an inlet and an outlet section, an inlet conduit for conveying dustladen air into the inlet section of said chamber, an exhaust conduit connected with the source of air suction for withdrawing air through said screen and from the outlet section to separate out dust particles on the surface of said screen for vacuum cleaner operation, means for agitating said screen, a pair of Valves for diverting the suction source from the exhaust conduit to operate the agitating means, electromagnetic means for actuating said valves, a circuit, means in said circuit for energizing the electromagnetic means, a switch in said circuit for closing and opening the circuit, pneumatic means responsive to a predetermined change in the air pressures within the inlet and outlet sections of the dust chamber to actuate said switch for closing said circuit, and means to actuate said switch to open the circuit after a predetermined time interval whereupon vacuum cleaner operation is restored.

11. In a vacuum cleaner, a source of air suction, a dust separating chamber, a dust screen in the chamber dividing it into an inlet and an outlet section, an inlet port for conveying dustladen air into the inlet section of said chamber, an exhaust conduit connected with the source of suction for withdrawing air through said screen and from the outlet section to separate out dust particles on the surface of said screen for vacuum cleaner operation, means for agitating said screen, an air turbine for operating said agitating means, a conduit connecting said turbine with said source of suction, valve means opening .said

exhaust conduit and closing the other conduit for said vacuum cleaner operation, said valve means being operable to close the exhaust conduit and open the other conduit for agitating operation, electromagnetic means for selectively positioning said valve means, a circuit including a source of current for energizing the electromagnetic means and switching means for closing and opening the circuit, and an air pressure operated device responsive to predetermined changes in the air pressures within the inlet and outlet sections of the dust chamber to actuate the switching means for closing said circuit.

12. In a vacuum cleaner, a source of air suction, a dust separating chamber, a dust screen in the chamber dividing it into an inlet and an outlet section, an inletport for conveying dustladen air into the inlet section of said chamber, an exhaust conduit connected with the source of suction for withdrawing air through said screen and from the outlet section to separate out dust particles on the surface of said screen for vacuum cleaner operation, means for agitating said screen, an air turbine for operating said agitating means, a conduit connecting said turbine with said source of suction, spring biased valve means normally opening said exhaust conduit and closing the other conduit for said vacuum cleaner operation, said valve means being simultaneously shiftable to close the exhaust conduit and open the other conduit for agitating operation, electromagnetic means for shifting said valve means against the spring bias, a circuit including a source of current for energizing the electromagnetic means and switching means for closing and opening the circuit, and an air pressure responsive device responsive to predetermined changes in the air pressures within the inlet and outlet sections of the dust chamber to actuate the switching means for closing said circuit, and means for determining the duration of operation of said turbine comprising a bellows chamber, a slow exhaustion device for said bellows chamber for controlling the duration of turbine operation, and means responsive to the exhaustion of the bellows for opening said circuit whereupon the spring bias returns said valve means to its normal position.

13. In a vacuum cleaner, a source of air suction, a dust separating chamber, a dust screen in the chamber dividing it into an inlet and an outlet section, an inlet port for conveying dustladen air into the inlet section of said chamber, an exhaust conduit connected with the source of suction for withdrawing air through said screen and from the outlet section to separate out dust particles on the surface of said screen for vacuum cleaner operation, means for agitating said screen, an air motor for operating said a itating means, means normally spring biased for maintaining vacuum cleaner operation and effective upon overcoming the bias for diverting the suction source from the outlet section to D- erate the air motor, said means comprising a pair of valves, simultaneously operable to connect the suction source to either the dust separating chamber or the air motor, a link for operatively positioning said valves, a solenoid for actuating said link, a circuit and a source of current for energizing the solenoid, and a switch for closing and opening the circuit, and an air pressure device responsive to predetermined changes in the air pressures within the inlet and outlet sections of said dust chamber to actuate the switch for closing the circuit whereby the dust and dirt accumulated on the dust screen is removed.

14. In a vacuum cleaner, source of air suction, a dust separating chamber, a dust screen in the chamber dividing it into an inlet and an outlet section, an inlet port for conveying dustladen air into the inlet section of said chamber, an exhaust conduit connected with the source of suction for withdrawing air through said screen and from the outlet section to separate out dust particles on the surface of said screen for vacuum cleaner operation, means for agitating said screen, and air motor for operating said agitating means, means normally spring biased for maintaining vacuum cleaner operation and effective upon overcoming the bias for diverting the suction source from the outlet section to operate the air motor, said means comprising a pair of valves, simultaneously operable to con nect the suction source to either the dust separating chamber or the air motor, a link for operatively positioning said valves, a solenoid for actuating said link, a circuit and a source of current for energizing the solenoid, and a switch for closing and opening the circuit, and an air pressure device responsive to predetermined changes in the air pressures within the inlet and outlet sections of said dust chamber to actuate the switch for closing the circuit whereby the dust and dirt accumulatedon the dust screen is removed, means for determining the duration of operation of said air motor comprising a bellows chamber, a slow exhaustion device connected to the suction source operating the air motor for collapsing the bellows chamber and means r esponsive to the exhaustion of the bellows chamber for opening said circuit whereby vacuum cleaner operation is restored.

15 A pneumatic switching device comprising a make and break switch, an air conduit divided into inlet and outlet portions, a porous membrane between said portions, an exhaust chamber, a diaphragm forming a wall of said chamber, means connecting said chamber to the outlet portion, a second exhaust chamber having said diaphragm in common with said first chamber, means connecting said second chamber to the inlet portion, means on said diaphragm contacting said switch and responsive to pressure differences of a predetermined amount in said conduit portions to actuate said switch to one position, and additional means for actuating said switch to another position after a predetermined time interval.

16. A pneumatic switching device comprising a make and break switch, an air conduit divided into inlet and outlet portions, a porous membrane between said portions, an exhaust chamber, a diaphragm forming a wall of said chamber, means connecting said chamber to the outlet portion, a second exhaust chamber having said diaphragm in common with said first chamber, means connecting said second chamber to the inlet portion, means on said diaphragm contacting said switch responsive to pressure differences of a predetermined amount in said conduit portions to actuate said switch to one position, a bellows, means for exhausting the bellows, means on the bellows contacting said switch and responsive to the exhaustion of said bellows to actuate said switch to another position.

17. A pneumatic switching device comprising a make and break switch, an air conduit divided into inlet and outlet portions, a filter member betwe n said portions, a pair of exhaust chambers, a diaphragm forming a wall of one of said chambers, a second diaphragm forming a wall of the other of said chambers, a third chamber formed in part by said diaphragms, means connecting the pair of chambers to the'outlet portion, means connecting the third chamber to the inlet portion, means on one diaphragm contacting said switch and responsive to a changein the air pressures of a predetermined amount insaid conduit portions to actuate said switoh,-said third chamber being effective to prevent suddensurges of air pressure from affecting the position of said switch actuating diaphragm.

18. A pneumatic switching device comprising a make and break switch, an air conduit divided into inlet and outlet portions, a filter member between said portions, a pair of exhaust chambers each sealed by a diaphragm, a third chamber between said pair of chambers and formed in part by said diaphragms, means connecting the pair of chambers to the outlet portion, means connecting the third chamber to the inlet portion, means on at least one of said diaphragms contacting said switch and responsive to pressure differences of a predetermined amount in said conduit portions to actuate said-switch to closed position, said third chamber being effective to prevent sudden surges of air pressure from affecting 16 the position of said switch actuating diaphragm, and additional means for actuating said switch to open position after havin remained closed for a predetermined time interval.

GUSTAF EINAR LOFGREN.

AXEL PETERSON.

REFERENCES CITED The following references are of record in th file of this patent:

UNITED STATES PATENTS Number Name Date 1,389,909 Skinner Sept. 6, 1921 1,538,292 Lindsay May 19, 1925 1,589,766 Schreiber June 22, 1926 1,715;273 Billings May 28, 1929 2,230,113 Hein Jan. 28, 1941 2,368,787 Skinner 1 Feb. 6, 1945 2,400,217 White May 14, 1946 2,443,162 Hallock June 8, 1948 2,500,832 Kirby May 15, 1950 FOREIGN PATENTS v Number Country Date 9,953 Great Britain Apr. 30, 1898 368,731 Great Britain Mar. 1, 1932 

